Collagen membrane



1. Collagen membrane

1.1 is an elevated perspective view of a collagen membrane;

1.2 is a top plan view thereof;

1.3 is a left side plan view thereof, the right side plan view being a mirror image of the left side plan view;

1.4 is a front plan view thereof; and

1.5 is a back plan view thereof. 

CLAIM The ornamental design for a collagen membrane, as shown and described. 